Class 4 (4th Engineer) MEKM 📅 Jul 2025

Exam Question

An auxiliary engine under load continuously fluctuates even with a steady load. The fault you diagnose could be owing to: (16)

(a) the quality of fuel

(b) the quality of servicing of the governor in the last port

(d) the overhaul of fuel injectors done in the last decarbonisation

Give a brief explanation as to why each of the above mentioned points either could be true or cannot at all be the reasons for such a fluctuation.

Reference Answer

The problem describes an auxiliary engine whose speed continuously fluctuates (a condition known as 'hunting') despite operating under a steady load. This indicates a fault in the engine's speed control system or a highly inconsistent fuel supply. We will analyze the four potential causes.
### (a) The Quality of Fuel
**This is a plausible, but less common, reason for speed fluctuation.**
* **General Effect of Bad Fuel:** Typically, poor quality fuel (e.g., high water content, high cat-fines, low cetane number) results in a consistent, steady-state problem. This would manifest as a general loss of power, high exhaust temperatures, incomplete combustion, and smoke. The engine would likely stabilize at a lower power output, but it would not continuously hunt.

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